Since scanning electron microscopy (SEM) provides an image resolution down to a few nanometers and a relatively high frame rate in comparison to atomic force microscopy, manipulators have been installed inside scanning electron microscopes (SEM) for the dissection, manipulation, or testing of samples at the nanometer scale. For instance, a nanomanipulator was built and used in tensile-loading individual carbon nanotubes inside an SEM in order to characterize their mechanical properties (M.-F. Yu, O. Lourie, M. J. Dyer, K. Moloni, Thomas F. Kelly, and R. S. Ruoff, “Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load,” Science, vol. 287, pp. 637-640, 2000). Also inside an SEM, a micromanipulator was employed to assemble prefabricated photonic plates into a novel three-dimensional photonic crystal (K. Aoki, H. T. Miyazaki, H. Hirayama, K. Inoshita, T. Baba, K. Sakoda, N. Shinya, and Y. Aoyagi, “Microassembly of semiconductor three dimensional photonic crystals,” Nat. Mater., vol. 2, pp. 117-121, 2003). U.S. Pat. No. 6,580,076 discloses a micromanipulation method for pick-and-place of micro objects with high repeatability inside an SEM.
Due to the aforementioned enabling capabilities, several nanomanipulation systems for SEM have been developed since 1970s by companies and university laboratories. Initially, a manipulator was mounted to either the specimen exchange chamber of an SEM (J. B. Pawley, “A dual needle piezoelectric micromanipulator for the scanning electron microscope,” Rev. Sci. Instrum., vol. 43, pp. 600-602, 1972) or a vacuum feedthrough on the chamber wall (I. Kawabata, Y. Nomura, and S. Shuto, “Microdissection within SEM using new micromanipulator,” J. Electron Microsc, vol. 30, pp. 85-88, 1981). In those two installation approaches, the XYZ driving elements of the manipulator were all located outside the specimen chamber while only the end effecter was inserted inside. Moreover, they both have the limitation that neither the specimen exchange chamber nor the feedthrough is able to accommodate more than one manipulator.
Since many applications of SEM nanomanipualtion require the collaboration of two or more manipulators, most present nanomanipulation systems have multiple manipulators mounted onto a platform/fixture which is fastened to the specimen stage inside an SEM. U.S. Pat. No. 6,891,170 and No. 7,220,973 B2 (Zyvex Corporation) disclose a manipulation system that includes one or more detachable manipulator modules coupled to a platform that interfaces with a microscope stage. Among several nanomanipulation systems developed by Zyvex Corporation, for example, the Zyvex S100 system contains four nanomanipulators and can be used for physical property characterization of nanomaterials (www.zyvex.com).
European Union Patents No. DE102007035950 and No. WO2008128532 (Klocke Nanotechnik) disclose a nanorobot module and an exchange adapter for fixing the nanorobot module to a vacuum stage. Similarly, Klcindiek Nanotechnik GmbH, Attocube Systems AG, and SmarAct GmbH also provide SEM nanomanipulation systems with multiple manipulator modules.
SEM nanomanipulation systems have also been developed in university laboratories, usually by assembling commercially available nanopositioning devices into a multi-degree-of-freedom manipulator. Since magnetic fields interfere with SEM imaging, piezoelectric elements are often used to build SEM-compatible actuators. U.S. Pat. No. 6,800,984 (Physik Instrumente GmbH & Co.) discloses a piezoelectric linear drive including a group of piezoelectric actuator stacks configured to drive a member located in a guidance device. U.S. Pat. No. 6,661,153 (Nanomotion Ltd.) discloses a method and apparatus for driving piezoelectric motors by exciting vibrations in a piezoelectric motor having a plurality of electrode sets. U.S. Pat. No. 6,476,537 and No. 6,707,231 (New Focus Inc.) disclose a method and apparatus for controlling a piezoelectric actuator coupled to a driven member. U.S. Pat. No. 5,568,004 and No. 5,994,820 (Kleindiek Nanotechnik GmbH) disclose electromechanical positioning devices based on piezoelectric actuators. Patent WO/2009/037693 (Piezo Nano-Technology Ltd) discloses a piezoelectric rotational motor based on the slick-slip principle.
As an example, by integrating piezoelectric actuators made by New Focus Inc., several SEM nanomanipulation systems with multiple motion units were built, such as (T. Fukuda, M. Nakajima, P. Liu, and H. ElShimy, “Nanofabrication, nanoinstrumentation, and nanoassembly by nanorobotic manipulation,” Int. J. Robot. Res., vol. 28, pp. 537-547, 2009), (D. Nakabayashi, P. C. Silva, and D. Ugarte, “Inexpensive two-tip nanomanipulator for a SEM,” Appl. Surf. Sci., vol. 254, pp. 405-411, 2007), and (M.-F. Yu, M. J. Dyer, G. D. Skidmore, H. W. Rohrs, X.-K. Lu, K. D. Ausman, J. R. Von Ehr, and R. S. Ruoff, “Three-dimensional manipulation of carbon nanotubes under a scanning electron microscope,” Nanotechnol., vol. 10, pp. 244-252, 1999). Different from manipulators being fixed onto a plate, a type of mobile microrobot actuated by piezoelectric discs was developed to move freely on a glass base plate mounted onto the SEM stage (A. Kortschack, A. Shirinov, T. Truper, and S. Fatikow, “Development of mobile versatile nanohandling microrobots: design, driving principle, haptic control,” Robotica, vol. 23, 419-434, 2005) (S. Fatikow, T. Wich, H. Hulsen, T. Sievers, and M. Jahnisch, “Microrobot system for automatic nanohandling inside a scanning electron microscope,” IEEE/ASME Trans. Mecha., vol. 12, 244-252, 2007). In comparison to fixed micromanipulators, this mobile microrobot has a larger workspace but a poorer positioning resolution.
To interact with a sample, an SEM nanomanipulator should carry an end-effector with both mechanical and electrical connections, such as a probe, AFM cantilever, or gripper. End-effectors are changed frequently primarily because they are prone to damage (e.g., bending and breakage). Since all existing SEM nanomanipulation systems are fastened inside the high-vacuum specimen chamber, exchanging end-effectors necessitates opening of the specimen chamber, which not only contaminates the chamber (thus worse imaging performance) but also incurs a lengthy, time-consuming pump-down process. Therefore, it is desirable if a nanomanipulation system can be transferred into and out of the specimen chamber without breaking the high vacuum.